Generally, an electronic product such as a liquid crystal display receives an alternating current (AC) voltage from a commercial power outlet via a power supply line. The AC voltage serves as a power supply signal to enable the electronic product to work. A power control key is usually employed in the electronic product to control a working state thereof. When the electronic product is turned off, the power supply line is not necessary to be pulled out from the commercial power outlet, a user merely needs to press down the power control key conveniently.
Take a conventional liquid crystal display as an example. The liquid crystal display includes a power control key and a controller. The controller can be a scaler having a control terminal, and the control terminal is grounded via the power control key. When the electronic product is turned off, the power control key is pressed down. This causes two ends of the power control key to be connected, and an electrical potential of the control terminal of the controller is pulled down. Detecting that the electrical potential of the control terminal is pulled down, the scaler controls driving circuits of a liquid crystal panel and an inverter circuit of a backlight system of the liquid crystal display to stop working. In this situation, the liquid crystal display is turned off.
However, because the power supply line of the liquid crystal display still remain being electrically coupled to the commercial power outlet, the power supply signal provided to the liquid crystal display is not cut off completely. This causes interface circuits of the liquid crystal display are still at work. The liquid crystal display may take power consumption about 0.1 W (watts) to 3 W all the same after being turned off via the power control key. Therefore, power waste is induced, and the power waste becomes serious particularly when the liquid crystal display maintains such a turn-off state for a long time. Accordingly power utilization efficiency of the liquid crystal display is low.
It is, therefore, desired to provide a power supply control circuit which overcomes the above-described deficiencies, and a liquid crystal display using such power supply control circuit.